The key question in the Watergate investigation echoes 40 years later with the New Jersey governor considered a top-tier contender for the 2016 Republican presidential nomination.

"There's so much coming out," Rep. Frank Pallone, D-N.J., said Friday on MSNBC's "PoliticsNation," referring to the former New Jersey official who ordered the closures charging that Christie knew of them at the time. "All of these things are making it more and more difficult for Governor Christie to run (for president)."

Mark Sokolich, the mayor of Fort Lee, N.J., and the man ostensibly targeted for political retiation in "Bridgegate" said Saturday on “Up w/Steve Kormacki” on MSNBC that the precise timing of when Christie learned of the lane closures is crucial.

“It essentially concludes that there was knowledge on part of the governor,” Sokolich said of the new account. “It doesn't say before. It says during the lane closures. … If during the lane closures means that Monday, Sept. 9, and no action was taken for the next four days, you know in my mind that's a big problem. … If he found out on Wednesday, still a problem. If he found out on Thursday, a problem, but less of one … than Monday.”

The new allegation arises in a letter to the Port Authority of New York and New Jersey (.pdf), from a lawyer for David Wildstein — the Port Authority official who last September actually ordered the closing of two of three local access lanes from Fort Lee, N.J., to the George Washington Bridge, one of the busiest bridges in the world.

In the letter, Wildstein's lawyer says "evidence exists tying Mr. Christie to having knowledge of the lane closures, during the period when the lanes were closed, contrary to what the Governor stated publicly in a two-hour press conference."

In a statement, Christie's office insisted that rather than call Christie's behavior into question, the letter "confirms what the Governor has said all along — he had absolutely no prior knowledge of the lane closures before they happened."

A new allegation claims New Jersey Gov. Chris Christie sanctioned a road closure as political payback. Michael Isikoff reports.

But the letter from Wildstein's lawyer never claims he knew about them beforehand. It accuses Christie instead of having known about them during the four days from Sept. 9 to Sept. 12, when traffic between New Jersey and New York was frozen.

That contradicts what Christie told reporters Jan. 9 in his marathon news conference.

"I had no knowledge of this — of the planning, the execution or anything about it — and I first found out about it after it was over," Christie said at the time.

To drive the point home, Christie's spokesman, Colin Reed, said late Friday night that "Governor Christie has said each time he has been asked that he first learned about the closing of the lanes on the George Washington Bridge from press accounts after the instance was over."

Discrepancies like that "certainly add to the speculation people have about the governor," said Assemblyman John Wisniewski, the Democratic co-chairman of the New Jersey legislative committee investigating the bridge scandal.

The letter goes on to say "Mr. Wildstein contests the accuracy of various statements that the Governor made about him" and ominously warns that "he can prove the inaccuracy of some."

Investigations so far have led to subpoenas for 17 Christie allies, his office and his re-election campaign, as well as abrupt unemployment for four associates who resigned or were fired, including Wildstein.

Wisniewski said on MSNBC's "Hardball" that Wildstein was among those who'd been served subpoenas, but he urged caution, saying the narrow wording of the subpoena could have allowed Wildstein to withhold crucial materials — meaning those materials could, indeed, exist.

"I don't know what these documents are that Mr. Wildstein or his attorney say that contradict the governor," Wisniewski said.

Republicans willing to speak about the new development were scarce Friday. But U.S. House candidate Steve Lonegan, who unsuccessfully challenged Christie for the Republican gubernatorial nomination in 2008, strongly defended the governor in an interview on Fox News.

Lonegan said it was immaterial whether Christie knew about the lane closings as they were happening: "Surprise, so did about 10 million other people."

What's missing in the Wildstein letter, he said, is a direct accusation that Christie knew why the lanes were closed.

"We never want to see abuse of power by any governor or any president, for that matter, but the governor has yet to be proven wrong," Lonegan said.

Democrats try to gain an edgeDemocrats were less reserved.

"It certainly seems Wildstein's attorney is suggesting the governor was not telling the truth," Pallone said.

Mo Elleithee, a spokesman for the Democratic National Committee, said Christie has "repeatedly said that he had no knowledge of the lane closures. Today's revelations raise serious questions about whether that is true."

Mel Evans / AP

David Wildstein after a hearing Jan. 9 at the New Jersey Statehouse in Trenton.

There are other echoes of Watergate: Christie's scandal has come to be known as "Bridgegate" and the investigation is uncovering other strands.

After the bridge scandal broke, Hoboken Mayor Dawn Zimmer told MSNBC that she had met with investigators and had turned over personal documents alleging that two Christie Cabinet members threatened to withhold relief aid for reconstruction after Hurricane Sandy unless she approved a redevelopment project favored by the governor.

A spokesman for Zimmer told NBC News on Friday that the U.S. attorney for New Jersey had served a subpoena on the city for documents relating to those allegations.

In March 2012 — just three months after a builder represented by Samson's law firm proposed a swanky new apartment complex along the Passaic River — Samson backed a $256 million plan to overhaul a nearby train station, the Record said, citing extensive records and interviews.

Samson's law firm is the same one that represented the development that Zimmer says she was pressured to support. Taken together, the incidents provoked public questions of conflicts between private interests and Christie's control over billions of dollars in public money.

But among those calling on people not to rush to judgment was Mark Sokolich — the Democratic mayor of Fort Lee, where the whole story started.

"I'm not rooting for the highest elected officer in the state of New Jersey to be part of this," Sokolich told MSNBC. "But there are still plenty of chapters to be written."